Near-field optical head

ABSTRACT

A near-field optical head has a tip end having an edge portion defined by two intersecting planes. Information recorded on a recording medium is reproduced in accordance with an intensity of scattered light of an evanescent field generated when the recording medium is illuminated with light and the tip end of the optical head is brought proximate the recording medium at an interval equal to or smaller than a wavelength of light therebetween.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a near-field optical head and, moreparticularly to a near-field optical head capable of promoting highresolution and enhancing a mechanical strength by devising a structureof a head, facilitating fabrication thereof and realizing highscattering efficiency of an evanescent field.

2. Background Information

At present, there has widely used an information reproducing device of areproduction exclusive type represented by a CD as well as a CD-ROM.According to the information reproducing device, information recorded onan optical disk is reproduced by using light. For example, in the caseof a CD, a surface thereof is recorded with pits each having a size ofsubstantially a wavelength of laser beam used in reproduction and adepth of substantially a quarter of the wavelength as recess andprojection information and the interference phenomenon of light isutilized for reproducing the information. When a spot of laser beam isilluminated onto the pit, since the depth of the pit is a quarter of thewavelength, a difference of optical paths of reflected light reflectedby a bottom face of the pit and reflected light reflected by the surfacebecomes a half of the wavelength of the illuminated laser beam.Therefore, the provided reflected light becomes weaker than that in thecase of irradiating the spot of laser beam onto a surface at other thanthe pit. In this way, by detecting the intensity of the reflected light,presence or absence of the pit is determined to thereby achievereproduction of information recorded on the optical disk.

In a system of irradiating the above-described laser beam and a systemof detecting thereof, a lens optical system used in a conventionaloptical microscope is used, however, the spot size of the laser beamcannot be made equal to or smaller than a half of the wavelength owingto a diffraction limit of light. Meanwhile, in order to increase aninformation recording density of the optical disk, the size of the pitmust be reduced and a track pitch must be narrowed. Accordingly, when aninformation recording unit is constituted by a size smaller than thewavelength of the laser beam, a conventional information reproducingapparatus cannot be used.

In view of such a problem, in recent years, there has been proposed anoptical memory utilizing technologies of a near-field opticalmicroscope. A near-field optical microscope uses a probe having a verysmall aperture of, for example, a diameter equal to or smaller than thewavelength of illuminated laser beam, for example, about one tenth ofthe wavelength and observes a very small surface structure and anoptical characteristic distribution of a sample by utilizing near-fieldlight (a nonpropagated component in light which exist in a region ofoptical wavelength or less from a surface of a substance: evanescentfield). According to such a near-field optical microscope, byirradiating propagated light from a rear face of the sample, thenear-field light is generated at the surface of the sample, the verysmall aperture of the probe and the surface of the sample are made toproximate to each other to a degree of the diameter of the very smallaperture of the probe and the near-field light is scattered at the verysmall aperture by which the near-field light is taken out from the verysmall aperture as propagated light. The near-field light generated atthe surface of the sample is accompanied by an intensity and a phasereflecting the very small structure and the optical characteristicdistribution of the surface of the sample and by processing thetaken-out propagated light by an optical detector, observation having aresolution which cannot be realized by a conventional optical microscopeis made feasible.

Further, a system of using an AFM cantilever provided with a sharpeningtreatment at its front end has frequently been used. There have beendescribed technologies of forming a light transmitting tip at a frontend of an AFM cantilever in a literature “Hulst et al., Appl. Phys.Lett. (1993) Vol. 62, p461”, a literature “Hulst et al., SPIE (1992)Vol. 1639, p36”, Japanese Patent Laid-Open No. 160719/1994 and PCTInternational Application Publication WO95/03561. Further, there havebeen described technologies of forming an AFM cantilever by a tip whichdoes not transmit light in a literature “Zenhausern et al., Appl. Phys.Lett. (1994) Vol. 65, p1623”, a literature “Bachelot et al.,Ultramicroscopy (1995) Vol. 61, p111” and Proceedings of Near-fieldOptics Research Group (“A reflective type near-field optical microscopeusing a metal probe and observation of a semiconductor sample having afine structure”, Proceedings of the 4th Symposium of Near-field OpticsResearch Group 1995, p53).

By applying the above-described near-field optical technologies to anoptical memory, information can be detected from an optical diskconstituted by an information recording unit of a wavelength of laserbeam or smaller.

However, according to the above-described method of forming a very smallaperture, formation of the very small aperture is difficult and a sizecapable of forming the aperture is provided with a limit and,accordingly, there poses a problem in which a resolution is difficult tobe improved to several tens nm or smaller. Meanwhile, according to theabove-described method of using an AFM cantilever, the front end issubjected to the sharpening treatment and therefore, the mechanicalstrength is weak and there poses a problem in which the reliability islow in using the AFM cantilever as a head. For example, the tip becomesliable to be damaged by the dust on a medium face or vibration of amedium. Further, many steps of a sharpening process are needed informing the tip and assuming the case of forming the tip at a flyinghead, there poses a problem in which heights of the flying head and thefront end of the tip are difficult to be matched. Further, a surfacearea of the tip is small and accordingly, there poses a problem in whichthe scattering efficiency of an evanescent field is lowered.

Hence, the invention has been carried out in view of the above-describeddrawbacks in the conventional art, and it is an object thereof toprovide a near-field optical head capable of improving a resolution andenhancing a mechanical strength, facilitating fabrication thereof andhaving a high scattering efficiency of an evanescent field.

SUMMARY OF THE INVENTION

According to an aspect of the invention, there is provided a near-fieldoptical head wherein in a near-field optical head for reproducinginformation recorded on a medium based on an intensity of scatteredlight of an evanescent field generated when a front end portion of ahead is made proximate to the medium at an interval of a distance equalto or smaller than a wavelength of light therebetween and light isilluminated to the medium, the front end portion of the head is formedin a shape of an edge in which two planes intersect with each other.

According to another aspect of the invention, there is provided anear-field optical head wherein in a near-field optical head forreproducing information recorded on a medium based on an intensity ofscattered light of an evanescent field generated when a front endportion of a head is made proximate to the medium at an interval of adistance equal to or smaller than a wavelength of light therebetween andlight is illuminated to the medium, the front end portion of the head isformed in a shape of an edge in which two planes intersect with eachother and a side thereof is microscopically provided with a radius ofcurvature.

According to another aspect of the invention, there is provided anear-field optical head wherein in a near-field optical head forreproducing information recorded on a medium based on an intensity ofscattered light of an evanescent field generated when a front endportion of a head is made proximate to the medium at an interval of adistance equal to or smaller than a wavelength of light therebetween andlight is illuminated to the medium, the front end portion of the head isformed in a shape of an edge in which two planes intersect with eachother, a side thereof is microscopically provided with a radius ofcurvature and the radius of curvature becomes infinitive at a sectionincluding the side in which the two planes intersect with each other.

According to another aspect of the invention, there is provided anear-field optical head wherein in a near-field optical head forreproducing information recorded on a medium based on an intensity ofscattered light of an evanescent field generated when a front endportion of a head is made proximate to the medium at an interval of adistance equal to or smaller than a wavelength of light therebetween andlight is illuminated to the medium, the front end portion of the head isformed in a shape of an edge in which at least one of the twointersecting faces is constituted by a curved face and a side where twofaces intersect with each other is provided with a radius of curvaturein a direction of a diameter of the medium.

Further, according to another aspect of the invention, there is provideda near-field optical head in the above-described near-field opticalhead, wherein the radius of curvature is set to be equal to or largerthan five times as much as the width of a bit of the medium.

Further, according to another aspect of the invention, there is provideda near-field optical head in the above-described near-field opticalhead, wherein one of the two faces constitutes a bottom face of aslider.

Further, according to another aspect of the invention, there is provideda near-field optical head in the above-described near-field opticalhead, wherein a light detecting element is arranged at an upper portionof the head.

Further, according to another aspect of the invention, there is provideda near-field optical head in the above-described near-field opticalhead, wherein a light detecting element is provided at a vicinity of thehead in the slider having the head.

Further, according to another aspect of the invention, there is provideda near-field optical head in the above-described near-field opticalhead, wherein a waveguide path is provided at a vicinity of the head andthe light detecting element is provided at the waveguide path in theslider having the head.

Further, according to another aspect of the invention, there is provideda near-field optical head in the above-described near-field opticalhead, wherein a metal film is provided over the entire or at a portionof the bottom face of the slider and the edge portion is formed by themetal film.

Further, according to another aspect of the invention, there is provideda near-field optical head in the above-described near-field opticalhead, wherein the slider having the head is constituted by a materialhaving transparency and the light source is arranged on the slider siderelative to the medium.

Further, according to another aspect of the invention, there is provideda near-field optical head in the above-described near-field opticalhead, wherein the slider having the head is constituted by the materialhaving transparency and the light source is provided to the slider.

Further, according to another aspect of the invention, there is provideda near-field optical head in the above-described near-field opticalhead, wherein the light source and the waveguide path for transmittinglight of the light source are provided to the slider having the head.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an outline perspective view showing a near-field optical headaccording to Embodiment 1 of the invention.

FIG. 2 is an enlarged side view showing a front end portion of the headshown in FIG. 1.

FIG. 3 is an enlarged front view showing the front end portion of thehead shown in FIG. 1.

FIG. 4 is an outline perspective view showing a modified example of thenear-field optical head shown in FIG. 1.

FIG. 5 is an outline perspective view showing a modified example of thenear-field optical head shown in FIG. 1.

FIG. 6 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 2 of the invention.

FIG. 7 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 3 of the invention.

FIG. 8 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 4 of the invention.

FIG. 9 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 5 of the invention.

FIG. 10 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 6 of the invention.

FIG. 11 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 7 of the invention.

FIG. 12 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 8 of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A detailed explanation will be given of the invention by referring tothe drawings as follows. Further, the invention is not limited by theembodiments.

(Embodiment 1)

FIG. 1 is an outline perspective view showing a near-field optical headaccording to Embodiment 1 of the invention. FIG. 2 is an enlarged sideview showing a front end portion of the head shown in FIG. 1. Thenear-field optical head 100 is provided with a constitution including ahead 2 in a projected shape disposed opposite to a disk 1 and a lightdetecting element 3 arranged above a front end portion of the head. Thehead 2 is provided with a beam portion 21 and a front end portion 22thereof is formed in an edge shape. An edge portion 23 of the front endportion 22 is constituted by a side 26 where a bottom face 24 and a sideface 25 of the head 2 intersect with each other. The bottom face 24 andthe side face 25 intersect substantially orthogonally to each other.When the edge portion 23 is viewed microscopically (nm level), the edgeportion 23 is provided with a curved face. A radius of curvature Rtthereof and a reproducible bit size correspond with each other and thesmaller (sharper) the radius of curvature Rt, the higher densityrecording can be carried out. The edge portion 23 can be fabricated byan angle determined by crystal faces when it is formed by usinganisotropic etching of Si. Further, also in respect of a material otherthan Si, a considerable sharpness can be realized by accurately settingetching conditions (regardless of wet etching or dry etching).

Further, the edge portion 23 is formed by intersecting two planes andthe angle of intersection poses no problem. For example, the edgeportion may be formed by intersecting two planes at an angle of 30degrees or 60 degrees. When a face vertically intersecting with a sideproduced by the two planes is defined as a section, the edge portion 23is provided with the same radius of curvature Rt even at any of thesection. Meanwhile, when a face including the side produced by the twoplanes is defined as a section, the radius of curvature is nullified. Incontrast thereto, according to the above-described conventional tip, anapex thereof is formed in a semispherical shape when it ismicroscopically viewed in any of a needle-like shape, a shape of acircular cone and a shape of a pyramid of the tip. Accordingly, when aface including the apex and a center of the spherical body is defined asa section, any of the section is provided with a radius of curvature.

The radius of curvature Rt of the edge portion 23 must be equal to orsmaller than the shortest bit length formed on the disk 1. When theradius of curvature Rt of the edge portion 23 is larger than a bitlength, presence or absence of a bit 11 can be read with excellent S/N.For example, when the bit length is 100 nm, the radius of curvature Rtof the edge portion 23 must substantially be smaller than about 100 nm.

Next, although a width W1 of the edge portion 23 may be larger than abit width on the disk 1, the width must not overlap a contiguous one ofa track 12. Further, although a wide width portion 27 (width W2) in aprojected shape may overlap a contiguous one of the track 12, in thatcase, a length L of the beam portion 21 may be provided to a degree ofpreventing cross talk from a contiguous one of the track 12.

Further, as shown in FIG. 3, the edge portion 23 per se may be providedwith a curvature (radius of curvature Rn). In this case, the bottom face24 is constituted by a curved face and by intersecting the bottom face24 with the side face 25, the edge portion 23 is formed. Also in such anedge portion 23, a radius of curvature Rt similar to that in FIG. 2 isprovided when it is viewed microscopically. The near-field optical head100 cannot track completely on the bit 11 and accordingly, a deviationin a direction orthogonal to the track is corrected by a feedbackcontrol. In this case, when the radius of curvature Rn in the directionorthogonal to the track is to a degree of the bit width, a signal(presence or absence of bit) by the feedback control in the directionorthogonal to the track becomes excessively large to thereby constitutenoise and the presence or absence of the bit in the direction of thetrack cannot be read as a signal. Accordingly, it is preferable to makethe noise smaller than the signal of the presence or absence of the bitin the direction of the track by about two orders even when the noise isreduced by a filter from a feedback frequency. Further, in view of thecurrent practical technical level (DVD or the like), the noise levelneeds to be smaller than the signal level by four orders or more. Fromthe above-described, although the radius of curvature Rn in thedirection orthogonal to the track is pertinent to be infinitive, itseems to pose practically no problem when the radius of curvature isabout five times as large as the bit width, preferably, fifty times ormore as much as the bit width.

Referring back to FIG. 2, a distance d between the edge portion 23 andthe disk 1 is controlled to be equal to or smaller than the wavelengthof light. In controlling the distance d, a so-to-speak flying head of ahard disk drive (HDD) is used and the near-field optical head 100 isflown by air film lubrication. When the fly head technology is used, aflow path in a shape of a wedge film needs to be formed by installing atapered face at the near-field optical head 100. According to the flyhead technology, the distance d can be controlled at around 50 nm.Further, as in the case of an AFM cantilever, the distance may bedetected and a feedback control may be carried out by a piezoelectricelement or the like. Further, the control may be realized by bringingabout a contact state interposing a thin lubrication film (oil or wateror the like) of about several nm therebetween or a complete contactstate may be brought about.

When light 4 is illuminated by an incident angle satisfying a totalreflection condition from a light source (illustration is omitted) to arear face of the disk 1, an evanescent field 41 is generated at thesurface of the disk. By inserting the edge portion 23 thereinto,scattered light 42 is generated. The optical intensity of the scatteredlight 42 is changed by presence or absence of the bit 11. The generatedscattered light 42 is received by the light detecting element 3. Thelight detecting element 3 carries out photoelectric conversion inaccordance with the optical intensity of the scattered light 42.Thereby, information on the disk 1 can be reproduced.

Further, the front end portion 22 of the head may be formed in a shapeof a sword as shown in FIG. 4 other than a shape of a short strip asshown in FIG. 1. Further, it may be formed in a circular shape as shownin FIG. 5. Further, in respect of a state of recording onto the disk 1,the bit may be recorded by using a difference in transmittance orreflectance or may be recorded as recess and projection. Further, thenear-field light includes far field light.

As mentioned above, according to the near-field optical head 100, incomparison with the conventional tip subjected to a sharpeningtreatment, the edge portion 23 is enhanced in the mechanical strengthand, accordingly, reliability of the near-field optical head isachieved. Next, in forming the tip, many steps of a sharpening processare needed, further, matching of heights of the front end of the tip anda slider is difficult in view of fabrication. In contrast thereto, theedge portion 23 can be formed comparatively easily at a portion of asupport mechanism head slider by an etching treatment and the matchingof heights of the edge portion 23 and a bottom face of the slider isdispensed with. Further, an area of scattering the evanescent field 41of the edge portion 23 is larger than that of the tip and accordingly,the provided intensity of scattered light is made stronger.

(Embodiment 2)

FIG. 6 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 2 of the invention. Thenear-field optical head 200 is constructed by a constitution which ismore specific than that of the near-field optical head 100 according toEmbodiment 1, mentioned above. According to the near-field optical head200, an edge portion 202 similar to the above-described (refer to FIG.2) is formed at a bottom face of a head slider 201. A tapered face 203is provided on a side thereof opposed to the edge portion 202. A flowpath in a shape of a wedge film is produced by the tapered face 203 anda disk 204. Further, formation of the edge portion 202 is carried out byan etching treatment. The near-field optical head 200 is supported by asuspension arm (illustration is omitted) and is driven by a voice coilmotor (illustration is omitted). Further, a lens 205 for condensingscattered light and a light detecting element 206 are arranged in askewed upper direction of the head slider 201.

When light 207 is illuminated from a light source (illustration isomitted) to a rear face of the disk 204 by an incident angle satisfyingthe total reflection condition, an evanescent field 208 is generated atthe surface of the disk. The head slider 201 is flown obliquely andaccordingly, the edge portion 202 approaches the face of the disk andscatters light. The optical intensity of scattered light 209 is changedby presence or absence of a bit 210. The generated scattered light 209is condensed by the lens 205. The light detecting element 206 isarranged at a condensing destination and the scattered light 209 isreceived by the light detecting element 206. The light detecting element206 carries out photoelectric conversion in accordance with the opticalintensity of the scattered light 209. Thereby, information on the disk204 is reproduced.

According to the near-field optical head 200, by carrying out theflying-head technology, the distance between the edge portion 202 andthe disk 204 can easily be controlled. Further, only the edge portion202 is formed at the head slider 201 and accordingly, the near-fieldoptical head 200 is more compact than a general magnetic head and thecost becomes lower.

(Embodiment 3)

FIG. 7 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 3 of the invention. Thenear-field optical head 300 is constructed by a constitution which ismore specific than that of the near-field optical head 100 according toEmbodiment 1 mentioned above. According to the near-field optical head300, an edge portion 302 similar to the above-described (refer to FIG.2) is formed at a bottom face of a head slider 301. Further, a steppedportion 303 is formed at a vicinity of the edge portion 302 in the headslider 301. A light detecting element 304 is provided at the steppedportion 303. A tapered face 305 is provided on the side thereof opposedto the edge portion 302. A flow path in a shape of a wedge film isproduced by the tapered face 305 and a disk 306. Further, formation ofthe edge portion 302 is carried out by an etching treatment. Thenear-field optical head 300 is supported by a suspension arm(illustration is omitted) and is driven by a voice coil motor(illustration is omitted).

When light 307 is illuminated from a light source (illustration isomitted) to a rear face of the disk 306 at an incident angle satisfyingthe total reflection condition, an evanescent field 308 is generated ata surface of the disk. The head slider 301 is flown obliquely andtherefore, the edge portion 302 approaches the face of the disk andscatters light. The optical intensity of scattered light 309 is changedby presence or absence of a bit 310. The generated scattered light 309is received by the light detecting element 304 provided at a vicinity ofthe edge portion 302 in the head slider 301. The light detecting element304 carries out photoelectric conversion in accordance with the opticalintensity of the scattered light 309. Thereby, information on the disk306 is reproduced.

According to the near-field optical head 300, the light detectingelement 304 is provided directly in the head slider 301 and accordingly,the head becomes compact. Further, by providing the light detectingelement 304 at the vicinity of the edge portion 302, the light detectingefficiency is improved.

(Embodiment 4)

FIG. 8 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 4 of the invention. Thenear-field optical head 400 is constructed by a constitution which ismore specific than that of the near-field optical head 100 according toEmbodiment 1, mentioned above. An edge portion 402 similar to theabove-described (refer to FIG. 2) is formed at a bottom face of a headslider 401. Further, a stepped portion 403 is formed at a vicinity ofthe edge portion 402 in the head slider 401. A light detecting element404 is provided at the stepped portion 403. Further, a metal film 405 isformed at a bottom face of the head slider 401. The edge portion 402 isformed by the metal film 405. Because the scattering efficiency of ametal edge is higher than that of an edge of a dielectric member.Further, the metal film may be formed not over the entire bottom face ofthe head slider 401 but only at the edge portion 402. A tapered face 406is provided on a side thereof opposed to the edge portion 402. A flowpath in a shape of a wedge film is produced by the tapered face 406 anda disk 407. Further, formation of the edge portion 402 is carried out byan etching treatment. The near-field optical head 400 is supported by asuspension arm (illustration is omitted) and is driven by a voice coilmotor (illustration is omitted).

At a portion where the head slider 401 is not present, light 408 isincident on the disk 407 by the total reflection condition andtherefore, all thereof is reflected. At a portion where the head slider401 is present (other than edge portion) with a distance equal to orsmaller than the wavelength from the disk 407, a distance between thehead slider 401 and the disk 407 is substantially equal to null andaccordingly, the light 408 penetrates the surface of the disk.Transmitted light (illustration is omitted) is reflected by the metalfilm 405 at the bottom face of the head slider 401. Or, when the metalfilm 405 is formed partially, light is reflected by a portion with themetal film 405. In this way, by reflecting light by forming the metalfilm 405 at the bottom face of the head slider 401, stray light enteringthe light detecting element 404 is reduced. Further, not the reflectingfilm but an absorbing film may be formed. However, it is not preferableto form the edge portion 402 by an absorbing film.

The principle of reproducing information is the same as that inEmbodiment 3. That is, the edge portion 402 of the flown head slider 401is made to enter an evanescent field 409 at the surface of the disk tothereby scatter light. The optical intensity of the scattered light 410is changed by presence or absence of a bit 411. The generated scatteredlight 410 is received by the light detecting element 404 provided at avicinity of the edge portion 402 in the head slider 401. The lightdetecting element 404 carries out photoelectric conversion in accordancewith the optical intensity of the scattered light 410. Thereby,information on the disk 407 is reproduced.

(Embodiment 5)

FIG. 9 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 5 of the invention. Thenear-field optical head 500 is constructed by a constitutionsubstantially the same as the near-field optical head 400 according toEmbodiment 4, mentioned above, and differs therefrom in that a waveguidepath is formed at the light detecting element. According to thenear-field optical head 500, an edge portion 502 similar to theabove-described (refer to FIG. 2) is formed at a bottom face of a headslider 501. A stepped portion 503 is formed at a vicinity of the edgeportion 502 in the head slider 501. A light detecting element 504 and awaveguide path 505 are provided at the stepped portion 503. A metal film506 is formed at a bottom face of the head slider 501. The edge portion502 is formed by the metal film 506. Because the scattering efficiencyof a metal edge is higher than that of an edge of a dielectric member.Further, the metal film 506 may be formed not over the entire bottomface of the head slider 501 but only at the edge portion 502. A taperedface 507 is provided on a side thereof opposed to the edge portion 502.A flow path in a shape of a wedge film is produced by the tapered face507 and a disk 508. Further, formation of the edge portion 502 iscarried out by an etching treatment. The near-field optical head 500 issupported by a suspension arm (illustration is omitted) and is driven bya voice coil motor (illustration is omitted).

When light 509 is illuminated from a light source (illustration isomitted) to a rear face of the disk 508 at an incident angle satisfyingthe total reflection condition, an evanescent field 510 is generated ata surface of the disk. The head slider 501 is obliquely flown andaccordingly, the edge portion 502 approaches the face of the disk andscatters light. The optical intensity of scattered light 511 is changedby presence or absence of a bit 512. The generated scattered light 511is received by the light detecting element 504 after having passedthrough the waveguide path 505 provided at a vicinity of the edgeportion 502 in the head slider 501. The light detecting element 504carries out photoelectric conversion in accordance with the opticalintensity of the scattered light 511. Thereby, information on the disk508 is reproduced.

According to the near-field optical head 500, the waveguide path 505 isformed on the light detecting element 504 and accordingly, the scatteredlight 511 from the edge portion 502 can selectively be guided to thelight detecting element 504. Accordingly, other scattered light does notenter the light detecting element 504 and therefore, an S/N ratio ispromoted. Further, a lens may be provided at a front end of thewaveguide path 505. Further, the light detecting element 504 is directlyprovided at the head slider 501 and accordingly, the head becomescompact. Further, by providing the light detecting element 504 at thevicinity of the edge portion 502, the light detecting efficiency isimproved. Further, light which has transmitted through the surface ofthe disk is reflected by the metal film 506 formed at the bottom face ofthe head slider 501. Therefore, stray light entering the waveguide path505 is reduced. In addition, scattered light produced by small defect,recess and protrusion or the like other than the bit on the disk 508 orlight which has transmitted through the head slider 501 or the likeconstitutes stray light, however, the waveguide path 505 is provided andaccordingly, influence of these stray light is difficult to be effected.

(Embodiment 6)

FIG. 10 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 6 of the invention. Thenear-field optical head 600 is constituted not by a system of totallyreflecting light at a surface of a disk but by a system of irradiatinglight from above a head slider. According to the near-field head slider600, a head slider 601 is constituted by a material having transparencyand an edge portion 602 similar to the above-described (refer to FIG. 2)is formed at a bottom face of the head slider 601. Further, a steppedportion 603 is formed at a vicinity of the edge portion 602 in the headslider 601. The stepped portion 603 is provided with a light detectingelement 604 and a waveguide path 605. A light source 606 and a lens 607are arranged on an oblique upper side of the head slider 601. A taperedface 608 is provided on a side thereof opposed to the edge portion 602.A flow path in a shape of a wedge film is produced by the tapered face608 and a disk 609. Further, formation of the edge portion 602 iscarried out by an etching treatment. The near-field optical head 600 issupported by a suspension arm (illustration is omitted) and is driven bya voice coil motor (illustration is omitted).

Light 610 from the light source 606 is condensed by the lens 607 andilluminates the edge portion 602 after having passed through the headslider 601. Accordingly, an evanescent field 611 is generated at asurface of the edge portion 602. The head slider 601 is flown obliquelyand accordingly, the edge portion 602 approaches a face of the disk andscatters light. The optical intensity of the scattered light 612 ischanged by presence or absence of a bit 613. Generated scattered light612 is received by the light detecting element 604 after having passedthrough the waveguide path 605 provided at a vicinity of the edgeportion 602 in the head slider 601. The light detecting element 604carries out photoelectric conversion in accordance with the opticalintensity of the scattered light 612. Accordingly, information on thedisk 609 is reproduced. According to the near-field optical head 600,the light source 606 is arranged on the same side with the head andtherefore, the apparatus can be made compact.

(Embodiment 7)

FIG. 11 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 7 of the invention.According to the near-field optical head 700, a head slider 701 isconstituted by a material having transparency and an edge portion 702similar to the above-described (refer to FIG. 2) is formed at a bottomface of the head slider 701. Further, a light detecting element 703 anda waveguide path 704 are provided at a vicinity of the edge portion 702in the head slider 701. A light source 705 and a lens 706 are integratedto the head slider 701. A tapered face 707 is provided at a side thereofopposed to the edge portion 702. A flow path in a shape of a wedge filmis produced by the tapered face 707 and a disk 708. Further, formationof the edge portion 702 is carried out by an etching treatment. Thenear-field optical head 700 is supported by a suspension arm(illustration is omitted) and is driven by a voice coil motor(illustration is omitted).

Light 709 from the light source 705 is condensed by the lens 706 andilluminates the edge portion 702 after having transmitted through thehead slider 701. Thereby, an evanescent field 710 is generated at asurface of the edge portion 702. The head slider 701 is flown obliquelyand accordingly, the edge portion 702 approaches a face of the disk andscatters light. The optical intensity of scattered light 711 is changedby presence or absence of a bit 712. The generated scattered light 711is received by the light detecting element 703 after having passedthrough the waveguide path 704 provided at the vicinity of the edgeportion 702 in the head slider 701. The light detecting element 703carries out photoelectric conversion in accordance with the opticalintensity of the scattered light 711. Accordingly, information on thedisk 708 is reproduced. According to the near-field optical head 700,the light source 705 and the lens 706 are integrated to the head slider701 and therefore, the constitution becomes compact. Further, theconstitution is suitable for mass production.

(Embodiment 8)

FIG. 12 is an outline constitution view showing a structure of anear-field optical head according to Embodiment 8 of the invention.According to the near-field optical head 800, an edge portion 802similar to the above-described (refer to FIG. 2) is formed at a bottomface of a head slider 801. Further, a light detecting element 803 and awaveguide path 804 are provided at a vicinity of the edge portion 802 inthe head slider 801. Further, a light source 805 and a waveguide path806 are integrated to the head slider 801. A tapered face 807 isprovided at a side thereof opposed to the edge portion 802. A flow pathin a shape of a wedge film is produced by the tapered face 807 and adisk 808. Further, formation of the edge portion 802 is carried out byan etching treatment. The near-field optical head 800 is supported by asuspension arm (illustration is omitted) and is driven by a voice coilmotor (illustration is omitted).

Light 809 from the light source 805 illuminates the edge potion 802after having passed through the waveguide path 806. Accordingly, anevanescent field 810 is generated at a surface of the edge portion 802.The head slider 801 is flown obliquely and accordingly, the edge portion802 approaches a face of the disk and scatters light. The opticalintensity of scattered light 811 is changed by presence or absence of abit 812. The generated scattered light 811 is received by the lightdetecting element 803 after having passed through the waveguide path 804provided at the vicinity of the edge portion 802 in the head slider 801.The light detecting element 803 carries out photoelectric conversion inaccordance with the optical intensity of the scattered light 811.Thereby, information on the disk 808 is reproduced. According to thenear-field optical head 800, only the edge portion 802 can beilluminated by the waveguide path 806 and therefore, stray lightentering the light detecting element 803 can be reduced. Further, thelight source 805 is integrated to the head slider 801 and therefore, theconstitution becomes compact. Further, the constitution is suitable formass production. Further, a lens may be arranged in front of the guidepath 806.

Further, although according to the above-described embodiments, anexplanation has been given of various means, members as well asstructures in a limited way, they can pertinently be modified within arange where the skilled person can design.

INDUSTRIAL APPLICABILITY

As has been explained, according to the near-field optical head of theinvention, the front end portion of the head is formed in a shape of anedge where two planes intersect with each other and therefore, themechanical strength of the head is enhanced and the reliability of thehead is promoted.

Further, according to the near-field optical head of the invention, thefront end portion of the head is formed in an edge shape in which atleast one of the two intersecting faces is constituted by a curved faceand a side where two faces intersect is provided with a curvature in adiameter direction of a medium. Preferably, the radius of curvature isset to five times or more of a bit width of the medium. Therefore, asignal in a direction orthogonal to a track does not constitute noiseand an S/N ratio sufficient for practical use is provided.

Further, according to the near-field optical head of the invention, oneof the two faces forming the edge constitutes a bottom face of a sliderand accordingly, there is no need of matching heights of a tip and aslider as in the case of forming the tip at the slider. Further, asharpening process is dispensed with, the edge portion can be formed byetching and therefore, fabrication thereof is facilitated.

Further, according to the near-field optical head of the invention, thelight detecting element is arranged at an upper portion of the head andaccordingly, the head becomes compact.

Further, according to the near-field optical head of the invention, thelight detecting element is provided at a vicinity of the head in theslider having the head and therefore, the head becomes compact and thelight detecting efficiency of scattered light is improved.

Further, according to the near-field optical head of the invention, theguide path is provided at a vicinity of the head in the slider havingthe head, the light detecting element is provided at the waveguide pathand therefore, only scattered light from the edge can selectively beguided to the light detecting element and therefore, the S/N ratio isimproved.

Further, according to the near-field optical head of the invention, themetal film is provided over the entire or at a portion of the bottomface of the slider and the edge portion is formed by the metal film.Light can be reflected at the bottom face of the slider and therefore,stray light can be reduced. Further, the edge is formed by the metalfilm and accordingly, the scattering efficiency is improved.

Further, according to the near-field optical head of the invention, theslider having the head is constituted by a material having transparency,the light source is arranged on the side of the slider relative to amedium and accordingly, the entire apparatus becomes compact.

Further, according to the near-field optical head of the invention, theslider having the head is constituted by a material having transparency,the light source is provided at the slider and accordingly, theconstitution can be made compact. Further, the near-field optical headis suitable for mass production.

Further, according to the near-field optical head of the invention, theslider having the head is provided with the light source and thewaveguide path for transmitting light of the light source andaccordingly, stray light entering the light detecting element can bereduced and therefore, the S/N ratio is improved.

What is claimed is:
 1. A near-field optical head for reproducinginformation recorded on a recording medium, comprising: an optical headhaving a tip end having an edge portion defined by two planesintersecting with each other, such that information recorded on therecording medium can be reproduced in accordance with an intensity ofscattered light of an evanescent field generated when the recordingmedium is illuminated with light and the tip end of the optical head isbrought proximate the recording medium at an interval equal to orsmaller than a wavelength of light therebetween.
 2. A near-field opticalhead for reproducing information recorded on a recording medium,comprising: an optical head having a tip end having an edge portiondefined by two planes intersecting with each other, a side of the edgeportion having a preselected radius of curvature, such that informationrecorded on the recording medium can be reproduced in accordance with anintensity of scattered light of an evanescent field generated when therecording medium is illuminated with light and the tip end of theoptical head is brought proximate the recording medium at an intervalequal to or smaller than a wavelength of light therebetween.
 3. Anear-field optical head for reproducing information recorded on arecording medium, comprising: an optical head having a tip end having anedge portion defined by two planes intersecting with each other, a sideof the edge portion having a preselected radius of curvature having amaximum at the point of intersection between the two planes, such thatinformation recorded on the recording medium can be reproduced inaccordance with an intensity of scattered light of an evanescent fieldgenerated when the recording medium is illuminated with light and thetip end of the optical head is brought proximate the recording medium atan interval equal to or smaller than a wavelength of light therebetween.4. A near-field optical head for reproducing information recorded on arecording medium, comprising: an optical head having a tip end having anedge portion defined by two surfaces intersecting with each other, aside of the edge portion having a preselected radius of curvature, andat least one of the intersecting surfaces being a curved surface, suchthat information recorded on the recording medium can be reproduced inaccordance with an intensity of scattered light of an evanescent fieldgenerated when the recording medium is illuminated with light and thetip end of the optical head is brought proximate the recording medium atan interval equal to or smaller than a wavelength of light therebetweenso that the radius of curvature of the side of the edge portion extendsin a diametrical direction of the recording medium.
 5. A near-fieldoptical head according to claim 4; wherein the radius of curvature ofthe side of the edge portion is equal to or larger than five times awidth of a bit of the medium.
 6. A near-field optical head according toclaim 5; further comprising a support mechanism for supporting theoptical head and for bringing the optical head proximate the recordingmedium, a lower surface of the support mechanism defining one of theintersecting surfaces.
 7. A near-field optical head according to claim5; further comprising a light detecting element disposed at an upperportion of the optical head.
 8. A near-field optical head according toclaim 6; further comprising a light detecting element disposed at avicinity of the optical head.
 9. A near-field optical head according toclaim 6; further comprising a waveguide path disposed at a vicinity ofthe optical head; and a light detecting element disposed in thewaveguide path.
 10. A near-field optical head according to claim 9;further comprising a metal film disposed over the entire or at a portionof a lower face of the support mechanism.
 11. A near-field optical headaccording to in claim 10; wherein the support mechanism is comprised ofa transparent material; and further comprising a light source disposedon the support mechanism.
 12. A near-field optical head according toclaim 6; wherein the support mechanism is comprised of a transparentmaterial; and further comprising a light source disposed on the supportmechanism.
 13. A near-field optical head according to claim 12; furthercomprising a light source and a waveguide path for transmitting lightemitted by the light source disposed on the support mechanism.
 14. Anear-field optical head according to claim 1; further comprising asupport mechanism for supporting the optical head and for bringing theoptical head proximate the recording medium, a lower surface of thesupport mechanism defining one of the intersecting surfaces.
 15. Anear-field optical head according to claim 14; further comprising alight detecting element disposed at a vicinity of the optical head. 16.A near-field optical head according to claim 14; further comprising awaveguide path disposed at a vicinity of the optical head; and a lightdetecting element disposed in the waveguide path.
 17. A near-fieldoptical head according to claim 14; further comprising a metal filmdisposed over the entire or at a portion of the lower face of thesupport mechanism.
 18. A near-field optical head according to claim 1;further comprising a light detecting element disposed at an upperportion of the optical head.
 19. A near-field optical head according toclaim 2; further comprising a support mechanism for supporting theoptical head and for bringing the optical head proximate the recordingmedium, a lower surface of the support mechanism defining one of theintersecting surfaces.
 20. A near-field optical head according to claim19; further comprising a light detecting element disposed at a vicinityof the optical head.
 21. A near-field optical head according to claim19; further comprising a waveguide path disposed at a vicinity of theoptical head; and a light detecting element disposed in the waveguidepath.
 22. A near-field optical head according to claim 19; furthercomprising a metal film disposed over the entire or at a portion of thelower face of the support mechanism.
 23. A near-field optical headaccording to claim 2; further comprising a light detecting elementdisposed at an upper portion of the optical head.
 24. A near-fieldoptical head according to claim 3; further comprising a supportmechanism for supporting the optical head and for bringing the opticalhead proximate the recording medium, a lower surface of the supportmechanism defining one of the intersecting surfaces.
 25. A near-fieldoptical head according to claim 24; further comprising a light detectingelement disposed at a vicinity of the optical head.
 26. A near-fieldoptical head according to claim 24; further comprising a waveguide pathdisposed at a vicinity of the optical head; and a light detectingelement disposed in the waveguide path.
 27. A near-field optical headaccording to claim 24; further comprising a metal film disposed over theentire or at a portion of the lower face of the support mechanism.
 28. Anear-field optical head according to claim 3; further comprising a lightdetecting element disposed at an upper portion of the optical head. 29.A near-field optical head according to claim 4; further comprising asupport mechanism for supporting the optical head and for bringing theoptical head proximate the recording medium, a lower surface of thesupport mechanism defining one of the intersecting surfaces.
 30. Anear-field optical head according to claim 29; further comprising alight detecting element disposed at a vicinity of the optical head. 31.A near-field optical head according to claim 29; further comprising awaveguide path disposed at a vicinity of the optical head; and a lightdetecting element disposed in the waveguide path.
 32. A near-fieldoptical head according to claim 29; further comprising a metal filmdisposed over the entire or at a portion of the lower face of thesupport mechanism.
 33. A near-field optical head according to claim 4;further comprising a light detecting element disposed at an upperportion of the optical head.
 34. A near-field optical head according toclaim 9; further comprising a metal film disposed over the entire or ata portion of the lower surface of the support mechanism.
 35. Anear-field optical head according to claim 1; further comprising awaveguide path disposed at the tip end of the optical head forpropagating the scattered light; and a light detecting element forreceiving the scattered light propagated by the waveguide path.
 36. Anear-field optical head according to claim 2; further comprising awaveguide path disposed at the tip end of the optical head forpropagating the scattered light; and a light detecting element forreceiving the scattered light propagated by the waveguide path.
 37. Anear-field optical head according to claim 3; further comprising awaveguide path disposed at the tip end of the optical head forpropagating the scattered light; and a light detecting element forreceiving the scattered light propagated by the waveguide path.
 38. Anear-field optical head according to claim 4; further comprising awaveguide path disposed at the tip end of the optical head forpropagating the scattered light; and a light detecting element forreceiving the scattered light propagated by the waveguide path.
 39. Anear-field optical head for reproducing information recorded on arecording medium, the near-field optical head comprising: an opticalhead having a tip end having an edge portion defined by two planesintersecting with each other; a support mechanism for supporting theoptical head and for bringing the optical head proximate a recordingmedium, a surface of the support mechanism defining one of theintersecting planes; and a metal film disposed over the entire or at aportion of the surface of the support mechanism.
 40. A near-fieldoptical head for reproducing information recorded on a recording medium,the near-field optical head comprising: an optical head having a tip endhaving an edge portion defined by two surfaces intersecting with eachother, a side of the edge portion having a preselected radius ofcurvature equal to or larger than five times a width of a bit of arecording medium, and at least one of the intersecting surfaces being acurved surface.
 41. In combination with a light source for illuminatinga recording medium with light, a near-field optical head for reproducinginformation recorded on the recording medium, the near-field opticalhead comprising: an optical head having a tip end having an edge portiondefined by two planes intersecting with each other; and a supportmechanism for supporting the optical head and for bringing the tip endof the optical head proximate the recording medium at an interval equalto or smaller than a wavelength of light therebetween so thatinformation recorded on the recording medium can be reproduced inaccordance with an intensity of scattered light of an evanescent fieldgenerated when the recording medium is illuminated with light by thelight source.
 42. A combination according to claim 41; furthercomprising a waveguide path disposed at the tip end of the optical headfor propagating the scattered light.
 43. A combination according toclaim 42; further comprising a light detecting element disposed at thetip end of the optical head for receiving the scattered light propagatedby the waveguide path.
 44. A combination according to claim 41; whereinthe support mechanism has a surface defining one of the intersectingplanes; and further comprising a metal film disposed over the entire orat a portion of the surface of the support mechanism.
 45. A combinationaccording to claim 41; wherein a side of the edge portion of the tip endof the optical head has a radius of curvature equal to or larger thanfive times a width of a bit of the recording medium.